1. Field of the Invention
The present invention relates to automatic seed planters of the type primarily intended for use in depositing seeds into standard seedling flats containing a growing medium. The seed planter of this invention is characterized by its provision of both an automatic dibbler and an automatic seed delivery system. The operation of both the dibbler and the seed delivery system is accomplished by a drive means which is adjustable to accommodate seedling flats of various size and configuration, and the cycle of the drive means is timed so as to provide dibbling of one flat while another, downstream flat has already been dibbled receives seeds. Finisher means are also disclosed for the addition of a relatively small quantity of growing medium onto the top of the seedling trays into which seeds have already been planted. Finally, vacuum means are also disclosed for efficiently removing and collecting unused seeds from the seed delivery system.
2. Description of the Prior Art
In the nursery industry, it is common practice to propagate young plants from seeds in seedling trays. While the dimension and configuration of seedling trays may vary, they are usually formed from a plastic material to comprise six individual compartments in two rows of three, each. It is further common practice to place twelve (12) of the trays in a carrier compartment for ease in planting, storing, and delivering to the wholesale customer. A significant cost of operating a seedling nursery involves the time and labor spent in preparing seedling trays for placement of the seeds therein. Not only is this operation lengthy, and therefore expensive when the seeds are deposited by hand, but also operating costs are invariably increased because of the inefficient delivery of the seeds to the flats by human operators. In this regard, it is to be noted that many of the seeds are of extremely small size such as, for example, petunia seeds.
Not surprisingly, then, automatic planting devices for delivering seeds to seedling flats have been developed and are known both in prior patent literature and in commerical use. For example, U.S. Pat. No. 4,106,414 to Vastag discloses an automatic seed-planting valve as an element of a seed planter for placing seeds in nursery flats. The invention comprises means for alternately applying vacuum and atmospheric pressure for individual seed application. A somewhat similar, air pressure device is disclosed in U.S. Pat. No. 3,738,530 to Fine. Other pressure-operated seed planters are also disclosed in U.S. Pat. No. 3,627,173 to Kerker and U.S. Pat. No. 3,986,638 to DeHart.
A conveyor belt-type automatic seed planting machine is disclosed in U.S. Pat. No. 4,010,778 to Aggen. According to the disclosure of the Aggen patent, seeds are delivered from a reservoir onto a first conveyor. From the first conveyor the seeds are then deposited onto a second conveyor moving at a speed greater than that of the first. The speed differential causes the seeds to become spaced apart one from another, and they are delivered from the second, faster conveyor onto the seed bed. U.S. Pat. No. 4,164,190 to Newman discloses a trailer-towed device including a roller which will form an array of shallow holes in the seed bed, followed by an array of seed delivery tubes for dropping seeds into the shallow holes formed by the roller. A similar implement is taught in the earlier U.S. Pat. No. 1,914,915 to Handler. In Wendt's U.S. Pat. No. 4,046,285 an apparatus is disclosed for diverting a supply of grains into a plurality of substantially parallel intermittent single flows of grain as for sowing one seed in each one of a number of plant growing pots. Finally, U.S. Pat. No. 4,072,251 to Huang discloses means used in combination with an automatic seed planter for singulating individual seeds from a reservoir and dispensing each seed into individual soil pots or cubes. Obviously, other automatic seed planting devices are known in the prior art, but those discussed above are believed to represent accurately the current state of the art. As one can immediately determine from a review of such prior art patents and currently available devices, significant limitations are present. For example, while certain ones of the prior art devices are certainly suitable for use in planting a field, because of their size and construction they would be of virtually no value in planting nursery seedling flats. Of the prior art devices which would be useful for planting seedling flates, almost all of them are relatively complex in that they rely upon pressure differentials for obtaining, placing and depositing the seeds. This is apparently a result of the heretofore unsolved problems associated with purely mechanical delivery of seeds by gravity. While the above patent to Huang does appear to address this problem, his solution is also relatively complex in that it requires a pair of independently reciprocating plates.
Accordingly, it is clear that there is a great need in the art for an efficient, reliable yet relatively simple means for planting nursery flats. Such a device would preferably prepare the flat for reception of the seed as by dibbling a receptacle into the growing medium placed within the flat, would then deliver seed to each prepared compartment of the flat, and would "top dress" the flat with additional growing medium. The construction of such a seed planter should be relatively simple and durable so that it could be operated by unskilled labor and would not require extensive preventive maintenance. Finally, and perhaps most importantly, it would also be desirable for such an automatic seed planter to be adjustable both with regard to the size and configuration of the seedling trays and with regard to the physical characteristics of the seed to be planted.